(a) Field of the Invention
The present invention relates to a four color display device, and in particular, to a display device having four primary color subpixels.
(b) Description of Related Art
Recently, flat panel display devices such as organic light emitting display devices, plasma display panel devices, and liquid crystal display devices have been widely developed.
A liquid crystal display (LCD) device is an example of a flat panel display device. The LCD device includes a liquid crystal (LC) panel assembly including an upper panel and a lower panel provided with two kinds of field generating electrodes such as pixel electrodes and a common electrode, and an LC layer with dielectric anisotropy interposed between the upper and lower panels. The pixel electrodes are arranged in a matrix and are electrically connected to switching elements such as thin film transistors (TFTs) to be sequentially applied with a data voltage for a row. The common electrode covers an entire surface of the upper panel and is supplied with a common voltage Vcom. The pixel electrode, the common electrode, and the LC layer form an LC capacitor, and the LC capacitor together with the switching element electrically connected to the LC capacitor is a basic unit of a subpixel.
A variation of a voltage difference between the field generating electrodes, i.e., a variation in the strength of an electric field generated by the field generating electrodes changes the transmittance of light passing through the LC panel, and thus desired images are obtained by controlling the voltage difference between the field generating electrodes.
The LCD device includes pixels, which each include three subpixels representing red, green, and blue colors, and displays colors using light from a light source provided with color filters representing red, green, and blue colors.
LCD devices are gradually being used for a wider variety of applications, and in particular, for television sets. Every possible effort is made in order to display colors similar to natural colors in the LCD devices used for television sets. For example, a trial has been undertaken in which color display capability is adjusted to a certain standard, for example, an EBU (Europe Broadcasting Union) standard, by increasing distribution density of a photoresist comprising color filters.
In such a case, a color sense of a blue filter representing the blue color is poor relative to other colors such as red and green. To remedy this, the color content ratio of a cold cathode fluorescence lamp (CCFL) used as a light source is adjusted to a higher luminance for the blue color.
However, the blue color has a high color temperature and thus has a tendency to change a color temperature of the entire CCFL, and thereby cyan, magenta, and yellow colors formed by a mixture of red, green, and blue colors look dark, unlike natural colors. In particular, a color sense of the cyan color is poor and thus a color display region is set to be a low temperature region. Accordingly, chroma of the cyan color is lowered relative to that of the yellow color or the magenta color. Additionally, a display capability for a low temperature color region increases, but in contrast, a display capability for a high temperature color region is decreased and thus the color display picture inclines to one side.